I have to say that it is not the dog or breed that makes them mean or aggressive. It is the people who choose to raise them that way. I've done research on this before for school. There is no thing as an aggresive gene, so dogs are not born aggressive. They are instead taught to be that way. There has also been no evidence that certain breeds are naturally more aggressive than others. Dogs like the Dachshund, Lhsa apso, and yorkshire terrier have attacked humans and have even caused death. Even a nice friendly dog of any breed can turn on someone if it has been abused or neglected. I have known several people with pit bulls and rottweilers. We used to own a pit bull, but had to get rid of him because we didn't have the time to take care of him. Every one of the dogs were friendly, family pets and even had children living with them. These dogs have been put in a stereotype and they can't speak to defend themselves. It is sad because pit bulls are the most euthanized dogs, mainly because of poor human judgement and responsibility. Dogs that have been rescued from these types of situations where they are raised to fight have to be euthanized because they are a dangerous risk. You never know what can trigger them and make them attack. They probably never knew a good happy life, and don't get the chance to have one. Very sad indeed.